Consider the following statements
I.Magnitudes of electron gain enthalpy proportional to Z effective
II.Magnitude of electron gain enthalpy proportional 1/atomic size
III.Magnitude of electron gain enthalpy proportional to penetrating power
Select the correct statement

Options

A. only I
B. Only II
C. II and III
D. all of these

Answer

To solve the question regarding the statements about electron gain enthalpy, we will analyze each statement one by one.

### Step 1: Understanding Electron Gain Enthalpy
Electron gain enthalpy (EGE) is defined as the amount of energy released when an electron is added to a neutral gaseous atom to form a negative ion. The more negative the value of EGE, the more favorable the process is.

### Step 2: Analyzing Statement I
**Statement I: Magnitudes of electron gain enthalpy proportional to Z effective.**

- Z effective (effective nuclear charge) is the net positive charge experienced by an electron in a multi-electron atom.
- A higher Z effective means that the nucleus has a stronger attraction on the added electron, which generally leads to a more negative electron gain enthalpy.
- **Conclusion**: This statement is correct.

### Step 3: Analyzing Statement II
**Statement II: Magnitude of electron gain enthalpy proportional to 1/atomic size.**

- Atomic size refers to the distance between the nucleus and the outermost electrons. As atomic size decreases, the added electron is closer to the nucleus and experiences a stronger attraction.
- Therefore, as atomic size decreases, the electron gain enthalpy becomes more negative (i.e., it increases in magnitude).
- **Conclusion**: This statement is correct.

### Step 4: Analyzing Statement III
**Statement III: Magnitude of electron gain enthalpy proportional to penetrating power.**

- Penetrating power refers to the ability of an electron to get close to the nucleus. Electrons in orbitals with higher penetrating power (like s-orbitals) experience a stronger attraction to the nucleus.
- Therefore, a higher penetrating power would lead to a more negative electron gain enthalpy.
- **Conclusion**: This statement is correct.

### Final Conclusion
All three statements are correct regarding the factors affecting the magnitude of electron gain enthalpy.

### Summary of Correct Statements
- I: Correct
- II: Correct
- III: Correct